The winning shot came on a crosscourt forehand. The replay system on Roddick's challenge confirmed the ball hit the outer portion of the sideline, and Del Potro raised both arms above his head in celebration.
It was the first loss for Roddick in four Washington finals. Roddick won the tournament in 2001, 2005 and 2007.
This was Roddick's first tournament since losing an epic Wimbledon final to Roger Federer on July 5. Roddick had taken a month-long break to recover from a hip injury.
Dixon becomes IRL career leader
Scott Dixon became IndyCar's leader in career victories after pulling away from the field to capture the Indy 200 at Mid-Ohio at Lexington.
The victory was Dixon's fourth of the season and 20th of his IndyCar career, breaking a tie with former series star Sam Hornish Jr.
Dixon entered the record books with ease, taking the lead from Justin Wilson halfway through the race then pouring it on to win by nearly 30 seconds over pole-sitter Ryan Briscoe.
The victory also pushed the defending points champion back atop the standings with four races left in the season.
The NASCAR Sprint Cup race at Watkins Glen (N.Y.) International was postponed because of rain and rescheduled for today.
A thunderstorm hit the track about 2 p.m. when drivers were about to start their engines. The course takes at least two hours to dry. Rain was still falling at 4 p.m, making it too late to complete the 90-lap event before sunset.
Blackhawks' Kane charged in attack
Chicago Blackhawks star Patrick Kane was charged with attacking a cab driver in his hometown of Buffalo, N.Y., a beating that police said was triggered when the driver did not have 20 cents in change to give the player and his cousin.
Buffalo police said the 20-year-old Kane and his 21-year-old cousin, James Kane, had apparently caught a cab from the city's downtown nightclub district at about 4 a.m. The cab driver suffered cuts to his face and his glasses were damaged, police spokesman Michael DeGeorge said.
Both men were charged with felony robbery and misdemeanor counts of theft of services and criminal mischief. Patrick Kane pleaded not guilty in City Court, WIVB-TV reported. It was not immediately clear when James Kane will appear in court.
Real Madrid routs D.C. United
Real Madrid beat D.C. United, 3-0, in an exhibition in front of 72,368 fans at FedEx Field in Landover, Md.
United goalkeeper Josh Wicks kept Real at bay in a scoreless first half, but Gonzalo Higuain scored twice in a two-minute span in the second half as the visitors took control. Arjen Robben scored the other goal for Real.
Salomon Kalou scored the winning penalty kick as Chelsea beat Manchester United, 4-1, in a shootout at Wembley, England, to clinch the Community Shield, the traditional opener to the English Premier League season.
The teams were tied, 2-2, after regulation.
Fowler selected for Walker Cup
Oklahoma State's Rickie Fowler, a former Murrieta Valley High standout, is among eight amateur players selected to the U.S. Walker Cup team.
The biennial Walker Cup matches, pitting an American team against a team representing Britain and Ireland, will take place Sept. 12-13 at Merion Golf Club in Ardmore, Pa.
England has pulled out of the badminton world championships in Hyderabad, India, after the tournament reportedly received a terrorist threat from a Pakistan-based Islamic militant group.